US4300919A - Apparatus and method for desorption of gas from a liquid - Google Patents

Abstract

An apparatus for desorption of gas from a liquid comprises a chamber and a pump for circulating liquid from the chamber through an external system and returning this liquid to the chamber. A part of the liquid delivered by the pump is used to power an aspirator in the chamber, the aspirator recirculating liquid within the chamber, resulting in desorption of gas which collects within the chamber for removal by known means. The rate of recirculation through the aspirator, and hence the rate of gas desorption, is thus not limited to the rate of flow through the external apparatus.

Description

This invention relates to apparatus and methods for desorption of gas from liquid, and is particularly intended for removal of entrained and dissolved air from liquid which is to be used in a hydraulic system.

It is known to desorb gas from a liquid by subjecting the liquid to a substantial reduction in pressure and collecting the gas which separates as a result. It is common practice to provide that the pressure reduction is to a subatmospheric level.

It is known, for example from U.S. Pat. No. 3,273,313, to provide an aspirator for inducing the required pressure reduction, this aspirator being powered by pressurized fluid which is delivered by a hydraulic supply pump for an external hydraulic system. In the foregoing reference, however, though the aspirator discharges liquid to a storage tank, it does not also serve to draw liquid from this tank, but draws liquid from a return line connected to an external apparatus. The rate of desorption is thus limited by the rate of flow through the external apparatus.

It is an object of the present invention to provide a desorption apparatus in which the rate of desorption is not limited by external flow conditions.

According to the invention an apparatus for desorption of gas from a liquid comprises a first storage chamber for said liquid, a pump for withdrawing liquid from said chamber, an aspirator having a nozzle to which liquid can be delivered by said pump, an aspiration inlet communicating with said chamber, and an outlet, said outlet also communicating with said storage chamber, and means for supplying to said chamber the liquid from which gas is to be desorbed.

In a particular embodiment said means for supplying liquid to said first chamber comprises a second chamber communicating with said first chamber adjacent said aspiration inlet, and means for permitting liquid flow from said aspirator outlet to pass to said second chamber.

According to another aspect of the invention a method of desorbing a gas from a liquid comprises withdrawing said liquid from a reservoir by means of a pump, supplying part of the liquid delivered by said pump to the nozzle of an aspirator which can also withdraw liquid from said reservoir, and returning liquid which is discharged from said aspirator to said reservoir, whereby the rate of fluid flow through said aspirator is not limited to the rate of flow from said pump to an external circuit.

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which:

FIG. 1 shows, diagrammatically a desorption apparatus and,

FIG. 2 shows, diagrammatically an alternative form of desorption apparatus.

As shown in FIG. 1 apump 10 can withdraw liquid from astorage chamber 11 and deliver this liquid through aline 12 to an external hydraulic system (not shown), liquid from the external system being returned to the upper end of thechamber 11 by way of aline 13. Apressure regulating valve 14 in theline 12 permits a part of the liquid delivered by the pump to be diverted to anaspirator 15 within thechamber 11.

Theaspirator 15 includes aconvergent nozzle 16 to which liquid is supplied at a pressure determined by thevalve 14. Thenozzle 16 is axially aligned with adivergent outlet 17 which is directed vertically upwardly into thechamber 11. Theaspirator 15 includes a plurality ofaspiration inlets 18 which are, as shown, adjacent the bottom of thechamber 11 and which open into a cavity 19 communicating with theoutlet 17 and surrounding thenozzle 16.

Theline 12 communicates with thechamber 11 by way of apressure relief valve 20. Shut-offvalves 21, 22 enable the arrangement to be isolated from the external hydraulic system.

The apparatus is intended for purging air from an external hydraulic system, for example that of an aircraft, and for desorbing air from hydraulic fluid within the external system. Thelines 12, 13 are respectively connected to pressure and return connections of the external system and thepump 10 delivers hydraulic fluid from thechamber 11 to the external system from which it eventually returns to thechamber 11. The portion of the hydraulic liquid flowing through thenozzle 16 is reduced in pressure to a subatmospheric level, causing liquid in the cavity 19 to be entrained and similarly reduced in pressure and pass upwardly through theoutlet 17. Liquid circulates within the tank, through theaspiration inlets 18, at a rate several times greater than that of the flow through thenozzle 16. Desorption of air from the liquid is thus very rapid and not dependent on the rate of flow through the external system, desorption continuing even if thevalves 21, 22 are shut. Desorbed gas passes upwardly to the surface of liquid within thechamber 11 and is withdrawn by avacuum pump 23 which maintains the chamber pressure subatmospheric.

A part of the gas within the fluid supplied through theline 13 will be desorbed as a result of its initial entry into the low pressure zone at the upper end of the chamber. The aspiration inlets 18, being adjacent the chamber bottom, thus receive liquid from which a proportion of the gas is already desorbed.

It is clearly desirable that the delivery pump should withdraw that part of the liquid from which the maximum amount of gas has already been desorbed. In conditions of rapid recirculation within thechamber 11 of FIG. 1, that is with thevalves 21, 22 shut, liquid reaching the inlet of thedelivery pump 10 may contain substantial quantities of entrained and dissolved air, thereby reducing the efficiency of the apparatus. The arrangement shown in FIG. 2 ensures that, in use the delivery pump receives liquid having a low air content.

As shown in FIG. 2 asupply pump 30 can draw liquid from achamber 31 and deliver it to an external hydraulic system through aline 32. Liquid can be returned from the external system to achamber 33 by way of aline 34. Anaspirator 35 comprises aconvergent nozzle 36 connected to receive liquid delivered by thepump 30. Theaspirator 35 further includes adivergent outlet 37 from thechamber 31, theoutlet 37 being aligned with thenozzle 36 and extending vertically upwardly into thechamber 33. Anannular space 38 between thenozzle 36 and an adjacent end of theoutlet 37 provides an aspiration inlet for liquid within thechamber 31.

The lower end of thechamber 33 communicates with thechamber 31 by way of aflow restricting valve 39 and apassage 40 which terminates adjacent theaspiration inlet 38. Arelief valve 41 is connected across thepump 30 andshutoff valves 42, 43 in therespective lines 32, 34 enable the apparatus to be isolated from an external system. Avent valve 44 is provided at the upper end of thechamber 33. The inlet of thepump 30 communicates with thechamber 31 at a lower part thereof.

In use, theaspirator 35 draws liquid from the upper portion of thechamber 31, the pressure inchamber 31 being reduced to below atmospheric pressure. This pressure reduction causes liquid to be withdrawn from thechamber 33 and to pass to the upper end ofchamber 31 through thevalve 39 andpassage 40. Liquid thus circulates continuously within thechambers 30, 31 through theaspirator 35. The low pressure maintained within thechamber 31 ensures that liquid in this chamber has a very low air content.

A part of the liquid leaving thepassage 40 passes through theaspirator inlet 38, the remainder of this liquid passing eventually to thepump 30. Thepump 30 thus withdraws liquid from thechamber 33, and returns part of this liquid to thechamber 33 by way external system.

Claims (6)

What is claimed is:

1. A method of desorbing gas from a liquid, comprising withdrawing liquid from a storage chamber by means of a pump, supplying a part of the liquid discharged by said pump to the nozzle of an aspirator whose outlet communicates with said chamber and which has an aspiration inlet communicating with said outlet by way of said chamber, supplying the remainder of said liquid discharged by said pump to an external circuit, and returning said remainder of the liquid from said external circuit to said storage.

2. An apparatus for desorption of gas from a liquid, comprising a first storage chamber for said liquid, a pump for withdrawing liquid from said chamber, an aspirator having a nozzle to which liquid can be delivered by said pump, an aspiration inlet communicating with said chamber, and an outlet, said chamber providing a flow path through which liquid can flow from said outlet to said inlet, first and second passages through which liquid can flow in parallel from said pump to said aspirator nozzle and to an external circuit, means for supplying to said chamber liquid returned from said external circuit, said means for supplying liquid to said first chamber comprising a second chamber communicating with said first chamber adjacent said aspirator inlet, and means for permitting liquid flow from said aspirator to pass from said first chamber to said second chamber.

3. An apparatus as claimed in claim 2 which includes a further pump for removing desorbed gas from said chamber.

4. An apparatus as claimed in claim 2 or claim 3 in which said aspiration inlet is adjacent the bottom of said chamber and said means for supplying the liquid communicates with an upper portion of said chamber.

5. An apparatus as claimed in claim 2 in which said aspirator outlet is divergent in the direction of flow therethrough and its smaller flow cross-section opens into said second chamber, said aspirator inlet being defined by a space between said smaller flow cross-section and said nozzle, and in which there is provided a passage communicating with said first chamber and extending to a location in said second chamber adjacent said aspirator inlet.

6. An apparatus as claimed in claim 5 which includes a flow restriction in said passage.

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